Synthesis of N-(2,3-dihydro-1-[14C]methyl-2-oxo-5-phenyl-1H-1, 4-benzodiazepin-3-yl)-benzamide and N-(2,3-dihydro-1-[14C]methyl-2-oxo-5-phenyl-1H-1, 4-benzodiazepin-3-yl)-N-[14C]methyl-benzamide as novelcarbon-14 labelled CCK antagonists

Article abstract of DOI:10.1002/jlcr.555

Two benzodiazepine CCK antagonists N-(2,3-dihydro-1-[¹⁴C]methyl-2-oxo-5-phenyl-1H 1,4-benzodiazepin-3-yl)-benzamide 2 and N-(2,3-dihydro-1-[¹⁴C]methyl-2-oxo-5-phenyl-1H-1, 4-benzodiazepin-3-yl)-[¹⁴C]methyl-benzamide 3 were synthesized in high yields through the reaction of N-(2,3-dihydro-2-oxo-5-phenyl-1H-1,4-benzodiazepin-3-yl)-benzamide 1 with [¹⁴C] methyl iodide in different situations. Copyright

Full text of DOI:10.1002/jlcr.555

JOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS
J Label Compd Radiopharm 2002; 45: 347–350.
DOI: 10.1002/jlcr.555
Research Article
1
4
Synthesis of N-(2,3-dihydro-1-[ C]methyl-2-
oxo-5-phenyl-1H-1,4-benzodiazepin-3-yl)-
benzamide and N-(2,3-dihydro-1-
1
4
[
C]methyl-2-oxo-5-phenyl-1H-1,
-benzodiazepin-3-yl)-N-[ C]methyl-
1
4
4
benzamide as novel carbon-14 labelled CCK
antagonists
1
,
2
Hojatollah Matloubi *, Ali Khalaj , Reza Dowlatabadi and
2,y
1
Gholamhossein Shirvani
1
Nuclear Research Center/AEOI, Chemical Division PO Box 11365-8486,
Tehran, Iran
2
Department of Medicinal Chemistry, Faculty of Pharmacy,
Tehran University of Medical Science, Tehran, Iran
Summary
1
4
Two benzodiazepine CCK antagonists N-(2,3-dihydro-1-[ C]methyl-2-oxo-5-
phenyl-1H 1,4-benzodiazepin-3-yl)-benzamide and N-(2,3-dihydro-1-
2
1
4
14
[
C]methyl-2-oxo-5-phenyl-1H-1,4-benzodiazepin-3-yl)-[ C]methyl-benza-
mide 3 were synthesized in high yields through the reaction of N-(2,3-dihydro-
1
4
-oxo-5-phenyl-1H-1,4-benzodiazepin-3-yl)-benzamide 1 with [ C] methyl
2
iodide in different situations. Copyright # 2002 John Wiley & Sons, Ltd.
Key Words: cholecystokinin antagonists; benzodiazepine; carbon-14; methyla-
tions
*
Correspondence to: H. Matloubi, Nuclear Research Center/AEOI, Chemical Division, PO Box
1365-8486, Tehran, Iran. E-mail: hmatloubi@seai.neda.net.ir
A part of Ph.D thesis.
1
y
Copyright # 2002 John Wiley & Sons, Ltd.
Received 3 September 2001
Revised 14 November 2001
Accepted 21 November 2001

3
48
H. MATLOUBI ET AL.
Introduction and discussion
Dealkylation and 3-hydroxylation are the most important metabolic
1
routes for several 1,4-benzodiazepine derivatives. Isotopic substitution
at the site of metabolic transformation is one of the best methods for
elucidating the mechanism of the metabolic process and several carbon-
1
4 labelled benzodiazepine derivatives have been synthesized and their
–6
1
metabolic fates studied in human and animal models.
Since the
isolation of the non-peptidal cholecystokinin (CCK) antagonist
7
Asperlicin, the 1,4-benzodiazepine ring system has served as a useful
tool for delineating the pharmacologic action of CCK.
In order to study the rate of 1-dealkylation of benzodiazepine CCK
antagonists and its influence on the pharmacologic profile of these
compounds it became necessary to synthesize a CCK antagonist derivate
labelled with carbon-14 at the N-1 position. Furthermore in order to
determine the rate of chain N-methyl dealkylation, synthesis of a ligand,
N-methylated both in N-1 and the amide chain appeared of interest.
1
4
The C labelling step in synthesis of 2 and 3 consists of methylation
1
4
8,9
of 1 with [ C] methyl iodide, prepared by the known methods from
1
barium [ C] carbonate via [ C] methanol. The benzodiazepine CCK
4
14
antagonist 1 was prepared through a benzotriazole-assisted synthetic
1
0
route from benzamide and 2-aminobenzophenone.
4
1
By utilization of molar equivalents of 1 and [ C] methyl iodide and a
short reaction time, the mono methylated product 2 in which only the
1
4
N-1 of the benzodiazepine ring is methylated, is obtained. Using [ C]
methyl iodide in excess and extending the reaction time yields the
dimethyl derivative 3.
Both compounds 2 and 3 were synthesized for the first time and their
1
13
structures were determined by IR, MS, H NMR and C NMR
spectroscopy.
Biological studies on these compounds are currently under investigation.
Copyright # 2002 John Wiley & Sons, Ltd.
J Label Compd Radiopharm 2002; 45: 347–350

NOVELL CARBON-14 LABELLED CCK ANTAGONISTS
349
Experimental
Radioactivity determinations were carried out with a liquid scintillation
counter (Beckman LS 6500) using an internal standard method. Thin
layer chromatography (TLC) analyses were carried out on silica gel
coated foils (Schleicher & Schull) and the spots visualized under UV
(
254 nm). Melting points were determined on a Reichert hot plate
1
apparatus and are uncorrected. H NMR and C NMR were recorded
13
1
on a Varian Unity Plus 400 spectrometer (399.866 MHz for H NMR
13
and 100.556 MHz for C NMR). Mass spectra were obtained on a
Finnigan TSQ-70 instrument. Infrared spectra were recorded on a
Nicolet Magna IR 550 spectrometer.
1
4
[
C] Methanol. According to a modification of the method of Cox
8
14
14
et al. [ C] carbon dioxide generated from [ C] barium carbonate
15.4 mCi, 0.197 g, 1 mmol) was introduced into a suspension of lithium
(
aluminium hydride (0.16 g, 4.2 mmol) in tetrahydrofurfuryloxy-tetra-
hydropyran (7 ml) and the mixture stirred for 1 h at room temperature.
Addition of tetrahydrofurfuryl alcohol (3.5 ml) and heating the system
at 1108C with passing a slow stream of nitrogen into the reaction
14
mixture gave [ C] methanol (14 mCi, 29.2 mg, 0.91 mmol). The latter
was stored in dry ice.
1
4
14
C] Methyl iodide. A solution of [ C] methanol (14 mCi, 29.2 mg,
[
0
3
.91 mmol) in 55% hydrogen iodide (4 ml) was heated at 40–908C for
0 min. Distillation of the reaction mixture by passing a slow nitrogen
1
4
stream and redistillation of the distillate on a vacuum line gave [ C]
methyl iodide (13.8 mCi, 28.8 mg, 0.9 mmol).
14
N-(2,3-Dihydro-1-[ C]methyl-2-oxo-5-phenyl-1-H1,4-Benzodiazepin-
-yl)-benzamide 2. Fresh sodium hydride (60% dispersion in mineral oil,
0 mg, 1 mmol) was added to a solution of 1 (355 mg, 1 mmol) in
3
4
anhydrous DMF (4 ml) at 08C under a nitrogen atmosphere. After 5 min
1
4
[
C] methyl iodide (15.3 mCi, 31.9 mg, 1 mmol) was added via a
micropipette and the reaction mixture stirred for 5 min. The reaction
mixture was then added to a vigorously stirred solution of water (25 ml)
containing aqueous sodium hydrogen sulfate (0.5 ml, 1 N).
The reaction slurry was filtered after 5 min and washed with water,
ether and cold methanol and dried under high vacuum. Recrystalization
from ethylacetate/n-hexan (6 : 4) gave pure 2 (12 mCi, 295 mg,
1
0
.8 mmol), m.p. 2428C, H NMR (d, CDCl ):3.51 (s, 3H, methyl), 5.71
3
(
d, 1H, J=8 Hz, CH), 7.38–7.63 (m, 12H, aromatics), 7.95 (d, 2H,
1
J=8 Hz, aromatics), 8.03 (d, 1H, J=8 Hz, amide NH) ppm; C NMR
3
Copyright # 2002 John Wiley & Sons, Ltd.
J Label Compd Radiopharm 2002; 45: 347–350

3
50
H. MATLOUBI ET AL.
(
d, CDCl ): 35.37, 67.58, 121.51, 124.55, 127.36, 128.22, 128.52, 129.13,
3
1
1
3
29.83, 130.67, 130.77, 131.76, 131.87, 134.00, 138.09, 142.80, 166.93,
67.41, 167.83; IR (KBr): n=691.9, 778.9, 1516.4, 1644.4, 1690.5,
052.6, 3277.9; mass: m/z=369.
14
N-(2,3-dihydro-1-[ C]methyl-2-oxo-5-phenyl-1-H1,4-Benzodiazepin-
1
-yl)-N-[ C]methyl-benzamide 3. Fresh sodium hydride (60% disper-
4
3
sion in mineral oil, 80 mg, 2 mmol) was added to a solution of 1 (355 mg,
mmol) in anhydrous DMF (4 ml) at 08C under a nitrogen atmosphere.
1
14
After 45 min [ C] methyl iodide (30.6 mCi, 63.8 mg, 2 mmol) was added
via a micropipette and the reaction mixture stirred for 45 min. The
reaction mixture was then added to a vigorously stirred solution of
water (25 ml) containing aqueous sodium hydrogen sulfate (0.5 ml, 1 N).
The reaction slurry was filtered after 5 min and washed with water,
ether and cold methanol and dried under high vacuum. Recrystalliza-
tion from ethylacetate/n-hexan (1 : 9) gave pure 3 (21.4 mCi, 268 mg,
1
0
3
7
3
1
1
2
.7 mmol), m.p. 1798C, H NMR (d, CDCl ): 3.45 (s, 3H, methyl),
3
.47(s, 3H, methyl), 6.18 (s, 1H, CH), 7.42-7.60 (m, 12H, aromatics),
1
.70 (d, 2H, J=8 Hz, aromatics) ppm; C NMR (d, CDCl ): 35.03,
5.35, 72.14, 121.73, 124.05, 127.21, 127.30, 128.24, 128.96, 129.59,
29.75, 130.22, 130.64, 131.83, 136.58, 138.26, 143.26, 166.61, 168.69,
72.56; IR (KBr): n=687.4, 1081.1, 1357.4, 1450.3, 1624.8, 1685.5,
921.2, 3267.9; mass: m/z=383.
3
3
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1
Copyright # 2002 John Wiley & Sons, Ltd.
J Label Compd Radiopharm 2002; 45: 347–350